NMR property calculations and experimental study of the 1,6-epoxycarvone and α-epoxypinene: a comparison of models.

This work aims at using theoretical calculations of shielding tensors (σ) through different methods [gauge-independent atomic orbital (GIAO), continuous set of gauge transformations (CSGT) and individual gauges for atoms in molecules (IGAIM)] and spin-spin coupling constants J using GIAO method to compare these methods and to corroborate the data obtained with the assignment of all of (1)H and (13)C NMR signals and the relative stereochemistry of the 1,6-epoxycarvone and the α-epoxypinene. All the (1)H and (13)C NMR signals were assigned unequivocally. The stereochemistry for the epoxides is trans and the B3LYP theory level with CSGT and IGAIM methods is the best choice to evaluate theoretical chemical shifts for compounds studied.

1H and 13C NMR spectral data of bioactive cage-like polycyclic compounds.

Bioactive cage-like polycyclic compounds have attracted the attention of several research groups because of their unique appearance and their biological activities. Their structures were established on the basis of (1)H NMR and (13)C NMR spectroscopic data. The (1)H and (13)C signal assignments and most homonuclear hydrogen coupling constants were assigned by use of techniques such as 1D (1)H and (13)C NMR and 2D gCOSY, non-edited gHSQC and gHMBC. The gNOESY experiments proved the endo-stereochemistry.

Stereochemistry of cyclopentane derivatives from (2,3)J(CH) dependence on dihedral angle (theta H--C--C--X).

The (2,3)J(CH) dependence on dihedral angle (theta H--C--C--X) for cyclopentane derivatives was investigated. We observed that the combined use of experimentally obtained (2,3)J(CH) values and the theoretically determined dihedral angles between the corresponding nuclei can be used to infer the relative stereochemistry of the ring substituents in cyclopentane derivatives. There is a good correlation between the magnitude of (3)J(CH) and the dihedral angle between the hydrogen and the coupled carbon (R2 = 0.88).

Antimicrobial activity and potential use of monoterpenes as tropical fruits preservatives.

Banana, papaya and pineapple are the most consumed tropical fruits in the world, being Brazil one of the main producers. Fungi Colletotrichum musae, Colletotrichum gloeosporioides and Fusarium subglutinans f.sp. ananas cause severe post harvest diseases and losses in fruits quality. The aim of this work was to evaluate the effectiveness of five monoterpenes to inhibit the mycelial growth and conidia germination of these three phytopathogens. The monoterpenes citral, citronellal, L-carvone, isopullegol and α-pinene were diluted in ethanol to final concentrations from 0.2 to 1%. All monoterpenes were found to inhibit the growth of the three studies fungi in a dose-dependent manner. Citral was the most effective of the oils tested and showed potent fungicidal activity at concentrations above 0.5%. Also, in vivo evaluation with these tropical fruits demonstrated the efficiency of citral to inhibit fungal growth. These results indicate the potential use of citral as a natural pesticide control of post-harvest fruit diseases.